1. Field of the Invention
The invention concerns a method for the improved image reproduction in reproduction technology, in particular in form manufacture.
2. Description of the Prior Art
For the obtaining of the color separations for multicolor printing, besides the classical method by means of cameras for copying work, to an increasing degree electronic devices are being used for the production of color separations, so-called scanners are used which undertake the color correction and the raster breakdown of the images or, respectively, of entire pages, which is necessary for the printing. Very often in such images or pages there are line drawings like scripts, edge cross pieces, signets, separation signs, frames etc. If one were simply to put such line drawing elements into the raster together with the half-tone images, then by means of the rastering at specific contours, a step-like distortion of the smooth line contours in the original would arise which in the printed reproduction has an unacceptably disturbing effect. Today customarily one obtains the color separations in such a manner than one only rasters the half-tone images in electronic devices or cameras. These half-tone separations are then mounted together with a film which carries the unrastered line drawing. From this mounting, on a third film, an intermediate negative is produced. This is again copied and provides a color separation which now bears the combination of rastered half-tone images and unrastered line drawings and is utilized for the production of forms. One is thus compelled to use this method which is expensive in terms of material and time, which in addition because of the many copying processes brings with it still a significant uncertainty in the total method if one wants to preserve the smooth contours of the line drawing in the rastered half-tone images all the way to the form.
One could indeed improve the line reproduction in the electronic devices in that one scans and records items of information, half-tone and line images, with multiple line fineness, for example, 2 to 3 times. However, in the case of the pre-given writing velocity, the processing time would rise proportionally with the refinement, which is also not acceptable for the practical operation. Besides this, in the case of the storage of entire images, an increased storage requirement arises.